We plan to initiate studies to determine the mechanism by which crude RLV polymerase can use viral RNA as template but purified enzyme cannot use purified 70S RNA. In vivo labeling experiments will be done to determine whether viral proteins are synthesized as high molecular weight precursors in the estrogen-stimulated uterus, as seems to occur in some in vitro systems. We will collaborate with Dr. Kouttab of our group to characterize an inhibitor of lymphocyte transformation in mouse uterus during gestation and to investigate its possible relationship to viruses.